This invention relates to a vent assembly for collapsible, flexible storage tanks; and in particular, to a vent assembly having an alternate attachment system for attachment to the tank and reduced mass and weight over prior art vents.
It is often desirable to have a container storage tank capable of holding a liquid such that when there is no liquid in the container, it may be collapsed or folded for ease of transportation and storage. Collapsible liquid containers have been available for some time and encompass a variety of designs. Also, it is common to provide a vent fixture or release valve in the collapsible storage tank to allow vapor and pressure that build up in the tank due to heat or agitation to be vented therefrom. This is of particular concern for collapsible storage tanks used to hold volatile fuel as the pressures and vapors contained in the tank may cause danger of explosion and/or fire if allowed to collect in the tank. Accordingly, allowing such vapors and pressure to vent is of prime importance.
One example of an early collapsible container of the pillow tank variety is found in U.S. Pat. No. 2,724,418 to Krupp, which is incorporated in its entirety herein by reference. Krupp discloses a flexible container that includes a volume responsive pressure relief valve and overflow valve assembly. In the Krupp disclosure, the pressure relief valve/vent is located in the middle and top of the tank. This is common in prior art tanks, as the top middle area tends to be the highest point and the location where gas, vapors, and pressure would rise to and presumably collect or be evacuated out of the pressure relief vent. In addition, the tank in Krupp includes a connector fitting, an attachable cap fitting for filling a drain in a tank. The tank also includes attached flexible handles. The containers are made from a flexible sheet material having an intermediate layer or a plurality thereof of square-woven textile fabric sheet material of cotton, nylon, rayon, glass fibers or other suitable filamentary material having the desired strength characteristics. The material is coated or treated with a suitable natural or synthetic rubber composition. The material may also include an outer protective layer of suitable rubber composition having age resisting and abrasion resisting characteristics, an inner layer of gasoline resistant rubber compositions, such as, for example, a copolymer of butadiene and acrylonitrile or a neoprene. The container is assembled by joining and adhering in a suitable known manner, including a plurality of pre-cut patterns of suitable flexible sheet material. The materials are joined in laterally extending seams of overlapped, fabric tape reinforced construction.
Another form of flexible container is found in U.S. Pat. No. 3,510,142 to Erke, which is incorporated in its entirety herein by reference. Erke discloses a portable, collapsible tank having an inflatable double walled construction with tie down means secured thereto. The tank in Erke has a double walled inflatable structure with one or more fill/drain ports. The tank is designed to receive and retain a variety of liquids or dry powder materials.
Another pillow tank is disclosed in U.S. Pat. No. 4,865,096 to Schober et al., which is incorporated in its entirety herein by reference. Schober et al. discloses a pillow tank with upper and lower sections, which are secured together along a seam extending around the mid section of the tank. A sleeve extends along a mid line of the entire perimeter of the seam. Slits or holes are formed through the sleeve to permit a rope to be threaded through portions of the sleeve to form tie-down points for the tank. The tank may also include exterior strapping in different configurations that can be sewn or secured to the tank for added strength. The tank is formed of a tube defined by an upper rectangular section and a lower rectangular section bonded together. Material for the tank may be typical elastomeric coated cloth panels, which may be square woven nylon cloth with a coating of neoprene or SBR rubber. Typical nylon cloth weights in a tank would be 5 and 13 ounces per square yard, although other weave patterns of nylon cloth can be used. Elastic coated aramid fibers may also be suitable material for manufacturing the tank.
Another flexible container is disclosed in U.S. Pat. No. 4,875,596 to Lohse, which is incorporated in its entirety herein by reference. The vessel in Lohse is designed for transporting or storing bulk materials or liquids and is shaped in the form of a tube having open ends tightly sealed by means of a straight line clamp or connection parts. The clamp connection parts are formed toothed rack-like so that, with relatively short clamp connections, tubes with relatively large openings can be sealed tightly.
U.S. Pat. No. 6,186,713 B1 to Bonerb discloses a bulk liquid freight transport vehicle, which is incorporated in its entirety herein by reference. The transport includes a collapsible liquid cargo bag and at least one adjustable cinching strap for being tightened down over the bag. Tightening of the strap over the bag causes the pressure of the liquid mass within the bag to increase to prevent motion of the liquid in the bag through motion of the vehicle.
A different type of flexible storage tank is disclosed in U.S. Pat. No. 6,842,955 B2 to Joshi et al., which is incorporated in its entirety herein by reference. The tank disclosed by Joshi et al. has a frusto-conical sidewall configuration and an open top. The tank is constructed of a material such as DuPont Elvaloy™, which is an ethylene-based polymer with reinforced synthetic fibers. Sections of the tank are joined using a heat sealing technique, such as radio frequency welding, ultrasonic heating, heating with hot air, electrical resistant heat, or other methods.
U.S. Patent Application Publication No. US 2009/0001085 A1 to Bartz et al. discloses a flexible tank, which is incorporated in its entirety herein by reference. The tank in Bartz et al. includes an internal baffle apparatus comprising a plurality of panel members connected along a connection line that defines an axis. Panel members extend in a diagonal fashion towards corners of the tank and also extending vertically between the top and bottom of the tank.
U.S. Pat. No. 7,717,296 B1 to Guthrie discloses a transportable and collapsible fabric tank with an integral balloon baffle system, which is incorporated in its entirety herein by reference. The tank in Guthrie is made from a fabric-composite-based material impregnated with polytetrafluoroethylene (PTFE). The internal baffles aid in the stability of the tank to prevent sloshing of the liquid while traveling with the tank partially filled. Internal baffles inflate to sizes large enough to force liquids out of the tank through the discharge valve.
One of the problems with prior art pressure relief and vent valves or fittings is that the assembly consisted of several members of substantial weight, and typically manufactured from metal. The members are held together with fasteners. The majority of the vent assembly was located external to the tank and tank material; however, typically there is also an internal portion of considerable overweight, such as is found in the patent to Krupp.
Accordingly, the weight of the vent or pressure relief assembly can cause tearing of the fabric material forming the wall of the tank in the area where it is attached. Additionally, the tank will have a tendency to sag in the area where the vent assembly is located based upon the weight of the assembly. Sagging can result in a small depression or concave area around the vent assembly. This concave area can collect moisture from rain, snow, and dew. As the concave area collects water, this further increases the weight around the vent assembly, causing an even greater depression and concave area. As should be appreciated, the weight and depression around a vent assembly can become quite significant.
In addition to the increased propensity for tearing around the valve assembly, the depression in concave area also prohibits all the gas and vapor pressure from being released through the vent assembly. Rather, the gas and vapor pressure can collect in an area around the vent assembly that becomes higher than the concave area associated with depression. As such, gas and vapors collect in a donut-shaped configuration around the vent assembly. These collected gas and pressurized vapors can present hazards and concerns as discussed above.
Accordingly, it is an object of the present invention to provide a vent assembly for a collapsible, flexible tank having less mass and weight than typical prior art assemblies to prevent sagging and tearing around the vent assembly. It is a further object of the invention to reduce the likelihood of tearing of the fabric around the weighted vent assembly. It is a further object of the invention to provide a vent assembly that reduces any concave depression around the vent assembly to prevent or reduce the amount of additional weight from accumulated water and moisture. These and other objects of the invention are encompassed in the invention and body of which is described in the detailed description and shown in the drawings.